FIG. 2 is a block diagram showing the arrangement of a solar power generation apparatus interconnected to a low-voltage distribution system.
A solar battery array 1 is constituted by combining a plurality of solar battery modules serially/parallelly so as to obtain a desired output voltage and current. Direct current power output from the solar battery array 1 is input to a system interconnect power converter 2 (to be referred to as a "power conditioner" hereinafter) where the direct current power is converted into alternate current power. The output of the power conditioner 2 is connected to a low-voltage distribution system 4 via a customer's ground fault interrupter 3. A load 5 is connected between the power conditioner 2 and the customer's ground fault interrupter 3. Wiring inside the customer's premises is wiring from the customer's ground fault interrupter 3 to the power conditioner 2 and load 5. The customer's ground fault interrupter 3 detects a ground fault current to detect an electrical leakage inside the customer's premises, and interrupts the connection between the customer's equipment and the low-voltage distribution system 4 so as not to influence the low-voltage distribution system 4 outside the customer's premises.
The solar battery array 1 has a ground capacitor 6. As a solar battery module constituting the solar battery array 1, built-in modules and low-profile modules have recently been developed. In some cases, a conductive member (metal plate or the like) as a reinforcing member or a conductive member such as a metal plate as a base member covers a roof. In this case, a solar battery cell and metal plate face each other at a small interval with a large area, which increases the ground capacitor 6. If water attaches to the surface and any area of a solar battery module owing to rain or the like, the ground capacitor 6 is ocurred by the water.
On the other hand, most of the system interconnect power conditioners 2 recently adopt a so-called transformerless method having no insulated transformer in order to attain high efficiency, small size, light weight, and low cost.
The present inventors have found that when the ground capacitor 6 is large, the system interconnect power conditioner 2 is of transformerless type, and a ground fault occurs outside the customer's premises, the ground fault current flows through the ground capacitor 6 of the solar battery array 1 and the power conditioner 2 to cause unwanted interruption operation in the customer's ground fault interrupter 3. This unwanted interruption operation generated in the customer's ground fault interrupter 3 causes a power failure inside the customer's premises though no electrical leakage occurs inside the customer's premises.
This problem is not limited to the solar power generation system. The same problem arises in a power generation system using a fuel cell if the ground capacitor is large. A ground fault outside the customer's premises causes the customer's ground fault interrupter 3 to unnecessarily perform interruption operation, which may generate a power failure inside the customer's premises.